(a) Field of the Invention
The present invention relates to a method and an apparatus for measuring activities of ions which are chemically specific in physiological fluids.
(b) Description of the Prior Art
There has already been known the fact that, among ions in physiological fluids, ions of sodium (Na), potassium (K), etc. play important rolls. Na and K ions, for example, occupy high ratios of the cations contained in blood and are the most important for maintaining adequate osmotic pressure and equilibrium between acids and bases groups in blood. Further, measurements of ions in blood which is a typical cellular fluids are very important since they permit comprehending conditions such as water contents, metabolism of electrolytes as well as excitability of nerves and muscles. Furthermore, variations of ion concentration in physiological fluids are highly significant in clinical diagnosis of diseases such as diarrhea, dehydration, cardiac insufficiency, vomiting, etc. While various ions in physiological fluids are measured for the reasons described above, the flame photometry and atomic absorption photometry have chiefly been utilized conventionally for measuring Na and K ions which are of special importance. However, these have posed many problems related to preparations, operations and installation required for measuring apparatus therefor. Furthermore, these methods could not assure measuring accuracy high enough for the above-mentioned purpose since they do not measure activities but quantities of ions contained in samples.
As another method for measuring chemically specific ions in physiological fluids mentioned above, there is known a method to use electrodes which responds selectively to ions to be measured. This method using such electrodes for measuring ions in physiological fluids had, however, a defect that it involved large errors in measured results or remarkably degraded determination accuracy when the physiological fluids or electrodes were contaminated. Further, physiological fluids, especially blood, should preferably be collected in quantities as small as possible since collection of large quantities of physiological fluids will give serious influences on human bodies. Therefore, physiological fluids available for measurements are generally in very small quantities and contamination will affects measuring accuracy remarkably.